This invention relates to compositions useful as collectors for the recovery of metal-containing mineral from ores by froth flotation.
Flotation is a process of treating a mixture of finely divided mineral solids, e.g., a pulverulent ore, suspended in a liquid whereby a portion of such solids is separated from other finely divided mineral solids, e.g., clays and other like materials present in the ore, by introducing a gas (or providing a gas in situ) in the liquid to produce a frothy mass containing certain of the solids on the top of the liquid, and leaving suspended (unfrothed) other solid components of the ore. Flotation is based on the principle that introducing a gas into a liquid containing solid particles of different materials suspended therein causes adherence of some gas to certain suspended solids and not to others and makes the particles having the gas thus adhered thereto lighter than the liquid. Accordingly, these particles rise to the top of the liquid to form a froth. The phenomena which renders flotation a particularly valuable industrial operation appear to be largely associated with the selective affinity of the surface of particulated solids, suspended in a liquid containing entrapped gas, for the liquid on the one hand, the gas on the other.
Various flotation agents have been admixed with the suspension to improve the frothing process. Such added agents are classed according to the function to be performed and include collectors such as xanthates, thionocarbamates and the like; frothers which facilitate the forming of a stable froth such as natural oils, e.g., pine oil and eucalyptus oil; modifiers such as activators, e.g., copper sulfate, to induce flotation in the presence of a collector; depressants, e.g., sodium cyanide, which tend to prevent a collector from functioning as such on a mineral which it is desired to retain in the liquid, and thereby discourage a substance from being carried up and forming a part of the froth; pH regulators to provide optimum metallurgical results, e.g., lime and soda ash and the like. The specific additives used in a flotation operation are selected according to the nature of the ore, the mineral sought to be recovered and the other additives which are to be used in combination therewith.
Flotation is employed in a number of mineral separation processes including the selective separation of such metal-containing minerals as copper, zinc, lead, nickel, molybdenum and other metals from sulfide minerals containing primarily iron, e.g., pyrite and pyrrhotite.
The conversion of metal-containing minerals to the more useful pure metal state is often achieved by smelting processes. Such smelting processes can result in the formation of volatile sulfur compounds. These volatile sulfur compounds are often released to the atmosphere through smokestacks, or are removed from such smokestacks by expensive and elaborate scrubbing equipment. Many nonferrous metal-containing minerals are formed naturally in the presence of sulfide minerals containing primarily iron, such as pyrite and pyrrhotite. When the iron-containing sulfide minerals are recovered in flotation processes along with the nonferrous metal-containing sulfide minerals and sulfidized metal-containing oxide minerals, there is excess sulfur present which is released in the smelting processes. Therefore, processes which selectively recover the nonferrous metal-contaning minerals while minimizing the recovery of the sulfide minerals containing primarily iron are desired.
Among others, collectors commonly used for the recovery of the metal-containing sulfide mineral ores or sulfidized metal-containing oxide minerals are xanthates, dithiophosphates, and thionocarbamates. Unfortunately, the xanthates, thionocarbamates, and dithiophosphates are not particularly selective in the recovery of nonferrous metal-containing sulfide minerals in the presence of sulfide minerals containing primarily iron. In addition, these collectors are not generally of a commercially acceptable quality in the recovery of oxide-containing mineral values.
Of the other collectors, the mercaptan collectors are very slow kinetically in the flotation of metal-containing sulfide minerals and the disulfides and polysulfides give relatively low recoveries with slow kinetics. Therefore, the mercaptans, disulfides and polysulfides are again not particularly selective in the recovery of nonferrous metal-containing sulfide minerals in the presence of sulfide minerals containing primarily iron.
In view of the foregoing, collectors which are useful for the recovery, at relatively good recovery rates and selectivities, of a broad range of metal-containing minerals from mineral ores, particularly metal-containing minerals from ores in the presence of sulfide minerals containing primarily iron are desired.